04 CR250r will not stop running

rudebarb69
Edited Date/Time 1/14/2016 7:56am
Hi guys, I am pretty new to this forum, so would just like hello to my fellow MX community, firstly.

I have just acquired a 2004 CR250r, it has not really been run in anger for a few years, so I cleaned the fuel system out, cleaned the carb, replaced the air filter, put a new sparkplug in and replaced the chain along with a few other little bits. I pulled her out at the weekend and fired her up, she ran well for around 10mins then I was about to switch her off, after turn the fuel stop tape off (just to drain the carb), she start to run at around half revs and wouldn’t turn off. I removed the HT lead and removed the CDI unit but I think the HT lead was still touching the engine and giving the spark to the sparkplug as she was still running. I removed the fuel line and after a minute or so (felt like hours, thought I was in for a full engine re-build) she stopped running. I noticed she drop a bit of coolant and there appeared to be a little bit of oil/fuel discolour (slight shine) in the coolant. Am I right in thinking that this would the gasket perished, allowing oil in to the engine which was keeping the bike running?

Any assistance and advice would be highly appreciated.
Thanks in advance
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garagedog
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garagedog 1/12/2016 12:35pm
1/12/2016 12:35pm
rudebarb69 wrote:
Hi guys, I am pretty new to this forum, so would just like hello to my fellow MX community, firstly. I have just acquired a 2004...
Hi guys, I am pretty new to this forum, so would just like hello to my fellow MX community, firstly.

I have just acquired a 2004 CR250r, it has not really been run in anger for a few years, so I cleaned the fuel system out, cleaned the carb, replaced the air filter, put a new sparkplug in and replaced the chain along with a few other little bits. I pulled her out at the weekend and fired her up, she ran well for around 10mins then I was about to switch her off, after turn the fuel stop tape off (just to drain the carb), she start to run at around half revs and wouldn’t turn off. I removed the HT lead and removed the CDI unit but I think the HT lead was still touching the engine and giving the spark to the sparkplug as she was still running. I removed the fuel line and after a minute or so (felt like hours, thought I was in for a full engine re-build) she stopped running. I noticed she drop a bit of coolant and there appeared to be a little bit of oil/fuel discolour (slight shine) in the coolant. Am I right in thinking that this would the gasket perished, allowing oil in to the engine which was keeping the bike running?

Any assistance and advice would be highly appreciated.
Thanks in advance
Warped head from the heat?

I would not run a 2 stroke out of gas on purpose. No fuel also means no lubrication too.


Mr Happy
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Mr Happy 1/12/2016 12:47pm
1/12/2016 12:47pm Edited Date/Time 1/12/2016 12:51pm
It reads like it ran without the HT lead attached to the plug. If so then it's dieseling and most probably running lean, like would if it were running out of fuel. Even with the HT lead removed and touching the cases the electrode is still isolated so it wouldn't spark.

A knackered head gasket wouldn't allow oil in to the cylinder on a two stroke, only on four stroke if there is an oil gallery near where it has failed and even then it would only run away if it were a diesel.
rudebarb69 1/12/2016 12:56pm
1/12/2016 12:56pm Edited Date/Time 1/12/2016 1:05pm
Good point Garagedog, what an idiot I am.

Mr Happy, not heard of dieseling before can you explain that to to me please? so it sounds like it would have been running lean as the fuel tap was turned off.

Also what would I need to do to rectify this?

Thanks guys
809
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809 1/12/2016 1:18pm
1/12/2016 1:18pm
Did you try to just put it in second or third and dump the clutch to kill it? Or was it revving too high?

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rudebarb69 1/12/2016 1:24pm
1/12/2016 1:24pm
809 wrote:
Did you try to just put it in second or third and dump the clutch to kill it? Or was it revving too high?
809, No I didn't try that, it was revving around 1/3 to half revs
Paw Paw 271
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Paw Paw 271 1/12/2016 1:28pm
1/12/2016 1:28pm Edited Date/Time 1/12/2016 1:30pm
I would also be looking for an air leak. Also did you clean out each of the jets in the carb? A dirty pilot jet can make it run lean and thus run hot.

Paw Paw
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Mr Happy 1/12/2016 1:33pm
1/12/2016 1:33pm Edited Date/Time 1/12/2016 1:36pm
rudebarb69 wrote:
Good point Garagedog, what an idiot I am. Mr Happy, not heard of dieseling before can you explain that to to me please? so it sounds...
Good point Garagedog, what an idiot I am.

Mr Happy, not heard of dieseling before can you explain that to to me please? so it sounds like it would have been running lean as the fuel tap was turned off.

Also what would I need to do to rectify this?

Thanks guys
Diesels are compression ignition engines i.e. they need no spark to burn fuel. If the air fuel mixture is far enough out and/or something in the cylinder is hot enough, spark plug, hot lump of carbon, cylinder wall, etc... then it will burn the fuel without a spark.

With the fuel tap off it could have been running lean enough. If it has stood for a long time it could have done in a crank seal. Could be the inlet perished. There are plenty of guides on the net to help you diagnose what it could be. A leak test would be a good start.
rudebarb69 1/12/2016 1:36pm
1/12/2016 1:36pm
Paw Paw 271 wrote:
I would also be looking for an air leak. Also did you clean out each of the jets in the carb? A dirty pilot jet can...
I would also be looking for an air leak. Also did you clean out each of the jets in the carb? A dirty pilot jet can make it run lean and thus run hot.

Paw Paw
I ran a carb cleaner through it so would have expected the jets to be cleaned out in the process, unless you can inform me different.

Thanks Paw Paw 271
rudebarb69 1/12/2016 1:38pm
1/12/2016 1:38pm
Mr Happy wrote:
Diesels are compression ignition engines i.e. they need no spark to burn fuel. If the air fuel mixture is far enough out and/or something in the...
Diesels are compression ignition engines i.e. they need no spark to burn fuel. If the air fuel mixture is far enough out and/or something in the cylinder is hot enough, spark plug, hot lump of carbon, cylinder wall, etc... then it will burn the fuel without a spark.

With the fuel tap off it could have been running lean enough. If it has stood for a long time it could have done in a crank seal. Could be the inlet perished. There are plenty of guides on the net to help you diagnose what it could be. A leak test would be a good start.
Thanks Mr Happy, much apprciated
Paw Paw 271
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Paw Paw 271 1/12/2016 6:10pm
1/12/2016 6:10pm
The pilot jets holes are so small that they can be plugged up and still look clear. Run a wire through the holes to be sure they are open. Carb cleaner and air will not clean them out after fuel has dried in the pilot jet.

Paw Paw
BobPA
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BobPA 1/12/2016 10:03pm
1/12/2016 10:03pm
Sounds like an air leak.

If it does it again hold it wide open, believe it or not it shuts them down.
therealVB99
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therealVB99 1/13/2016 12:34pm
1/13/2016 12:34pm
rudebarb69 wrote:
Hi guys, I am pretty new to this forum, so would just like hello to my fellow MX community, firstly. I have just acquired a 2004...
Hi guys, I am pretty new to this forum, so would just like hello to my fellow MX community, firstly.

I have just acquired a 2004 CR250r, it has not really been run in anger for a few years, so I cleaned the fuel system out, cleaned the carb, replaced the air filter, put a new sparkplug in and replaced the chain along with a few other little bits. I pulled her out at the weekend and fired her up, she ran well for around 10mins then I was about to switch her off, after turn the fuel stop tape off (just to drain the carb), she start to run at around half revs and wouldn’t turn off. I removed the HT lead and removed the CDI unit but I think the HT lead was still touching the engine and giving the spark to the sparkplug as she was still running. I removed the fuel line and after a minute or so (felt like hours, thought I was in for a full engine re-build) she stopped running. I noticed she drop a bit of coolant and there appeared to be a little bit of oil/fuel discolour (slight shine) in the coolant. Am I right in thinking that this would the gasket perished, allowing oil in to the engine which was keeping the bike running?

Any assistance and advice would be highly appreciated.
Thanks in advance
garagedog wrote:
Warped head from the heat?

I would not run a 2 stroke out of gas on purpose. No fuel also means no lubrication too.


X2^

That trick is for 4 strokes only.. No premix.
scooter5002
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scooter5002 1/13/2016 4:39pm
1/13/2016 4:39pm
Sorry to burst the bubble, but running the carb dry does not hurt the engine, due to lack of lubication. Ever take the top end off, spin the crank, and see oil on the bottom of it? Ya, it's in there. Same with the bearings, they're wet with oil. Do it to my bike all the time, if I think I won't be on it for a while. Never hurt anything, and if I yank the jug, everything is oiled down below. I run a 40:1 mix, too.
Mr Happy
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Mr Happy 1/13/2016 5:10pm
1/13/2016 5:10pm
You could just open the drain or remove the plug in the float bowl to drain the carb. Takes less time to drain it that way than running it out of fuel.
Hondas4Life3
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Hondas4Life3 1/13/2016 11:42pm
1/13/2016 11:42pm Edited Date/Time 1/13/2016 11:44pm
Air leak the exact same thing happened to my 05. The left side crank seal probably needs replaced (thats what mine needed). Use two fine screws and screw them into the seal just far enough to grab the threads and pull it out. Be careful. If the air leak was that bad it may have sucked in dirt and ate the crank bearings, happened to me.

Invest in a leak down tester
Stooperbike
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Stooperbike 1/14/2016 7:56am
1/14/2016 7:56am
Just going to add my 2 cents because I have had a strange issue with a few of the CRs I have had. I have an 02, while riding one day it felt like the throttle got stuck open so I pulled in the clutch and pushed the kill switched, nothing happened, it just kept running, wicked scary! It felt like the others were saying, it was dieseling, but it was also panic situation! But what I did was to safety wire the little boot that holds the cable into the top of the carb. I thought maybe the cable somehow got hung up outside the its housing in the carb. I put safety wire around bottom of the boot that holds the throttle cable in the top of the carb, then safety wired the top of the boot to the cable. This way the cable is not going to come out. I don't think this is what you have going on but just throwing it out there.

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